Tectonics and Depositional Systems of Trinidad and Tobago Deepwater Provinces: Petroleum Systems Implications and Prospectivity

Abstract

The deepwater provinces of the Columbus Basin are the focus of recent exploration activity to prove the extension of the commercial hydrocarbon trend from the prolific foreland basin systems of onshore and eastern offshore Trinidad. In the onshore Southern Basin, >1.5 billion barrels of oil have been produced in over ~100 years of petroleum exploration and production. The eastern offshore Columbus Basin shelf has yielded >1 billion barrels of oil and 15 trillion cubic feet of gas since the first commercial discovery in 1968. The findings of deepwater exploration campaigns provide evidence for well-developed sand units with good reservoir properties, competent trapping mechanisms and a working thermogenic system in the basin, however there have been no commercial discoveries to date.

We use an integrated geoscience data set including ~10,000 line kilometers of 2D seismic reflection lines recorded to depths > 12 seconds TWT, well data, satellite gravity, heat flow and geochemical observations to evaluate the petroleum system and plays within the deepwater area. The deepwater provinces are located within a complex zone of transition from an intensely thrusted range and foreland basin associated with Miocene collision, to the active contractional accretionary prism at the leading edge of the Caribbean plate. Potential reservoirs are contained within Pleistocene to Palaeogene slope and basin floor fan systems. Syndepositionally active contractional structures influence sediment pathways and reservoir distribution. Structures including thrust faults and thrust-cored anticlines with some associated diapirism form potential traps; structurally conformable amplitude anomalies have been observed. The source rock for the proven Southern and Columbus basins is contained within bituminous mudstones, shales, marls and limestones of the Cretaceous Naparima Hill Formation. While the Naparima Hill Formation has not been drilled in the Columbus Basin due to burial depths, it is the accepted source for produced thermogenic hydrocarbons in the basin.

We review the basin history in the context of petroleum systems events including; depositional systems, the timing potential trap formation, the continuity and viability of the proven source rock into the deepwater provinces, and the timing of crustal deformation and loading on burial and thermal history of the source rock, in a discussion of the key risks and uncertainties associated with the deepwater petroleum system.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018